Photo provided to the TImes Observer Forest Service State, Private, and Tribal Forestry staff, Danielle Kelley, prepares to release a biocontrol for hemlock woolly adelgid on the Allegheny National Forest.

Forest Service officials are using one bug to combat another bug on the Allegheny National Forest.

The ANF announced this week that “biological controls” have been released in recent weeks to combat the spread of hemlock woolly adelgid (HWA).

“Biological control is the use of a natural predator, parasitoid or pathogen to manage pest populations,” ANF Public Affairs Officer Christopher Leeser said.

There are four possible biocontrols for HWA. Species of silver flies, “native to the Pacific Northwest and Japan, where HWA is a common pest of local hemlocks” have been released at several locations in the Bradford District of the ANF.

Per the Forest Service, 1,000 were released above Nelse Run stream in early May. That was followed in mid-May by 2,100 near Kiasutha Recreation Area.

An additional 1,500 were released “to augment the prior release near the Nelse Run stream,” according to the ANF.

HWA is an invasive insect that poses a significant threat to hemlock trees.

“Laricobius beetles are released as adults in the fall and feed exclusively on developing and adult HWA throughout the fall and winter while the adelgid is in the first of two annual generations,” Leeser explained. “Leuco Taraxis flies are released as adults in the spring, with larvae preying on HWA eggs throughout the adelgid’s laying season.

“When present on the same site in sufficient numbers, the two biocontrols work in tandem for increased predation across multiple HWA life cycle stages.”

Flies were released near Tuttle Run and Willow Creek in spring 2023 while beetles were released near Baughman Run that fall.

“All flies and beetles were provided by Cornell University and Virginia Tech, with essential technical support from US Forest Service State, Private, and Tribal Forestry,” Leeser said.